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N Stebbing

Publications and source records attributed to N Stebbing.

At least 19 recordsLinked to original sources
PubMed1989

Induction and depression of cytochrome P-450-dependent mixed-function oxidase by a cloned consensus alpha-interferon (IFN-alpha CON1) in the hamster.

A novel analogue of human alpha-interferon (IFN-alpha CON1) was tested for its ability to modify the hepatic cytochrome P-450-dependent mixed-function oxidase system in the hamster. This cloned interferon was derived by selecting the most frequently observed amino acid sequences at each position in the known human alpha-interferon subtypes. IFN-alpha CON1 had a biphasic effect on cytochrome P-450 and related drug biotransformation in the hamster causing an initial increase followed by a significant depression. IFN-alpha CON1 also had a biphasic effect on cytochrome P-450 in the lung, adrenal and spleen but only a depressant effect in the kidney. This effect was not due to morphological damage and followed the species specificity for this type of interferon. Both the increase and the decrease in cytochrome P-450 could be prevented by the administration of the protein synthesis inhibitor puromycin. Various isozymes of cytochrome P-450 induced by phenobarbital, beta-napthaflavone and clofibrate were also depressed by this interferon. The results presented in this report suggest that IFN-alpha CON1 interferon will likely depress drug biotransformation in humans because the antiviral effects and the "anti-cytochrome P-450" effect of interferons cannot be separated, and this interferon has antiviral properties in both hamster and human cells. Clinically relevant drug interactions may be common during the concomitant use of this interferon and other drugs that are metabolized by cytochrome P-450.

Animals↗
PubMed1989

The role of three domains in the biological activity of human interferon-alpha.

Earlier studies showed that minor differences in primary structure among the interferon-alpha (IFN-alpha) protein family are reflected in their potency in selected biological assays. These studies have been extended and results from assays of antiviral, growth inhibitory and 2',5'-oligoadenylate (2-5A) synthetase activities indicate that the various novel hybrid and analog species are differentially biologically active. Overall these observations suggest a correlation between predicted secondary structure characteristics, receptor binding affinity, and 2-5A synthetase, antiviral and growth inhibitory activities. Studies with a consensus IFN-alpha analog particularly implicated the region around residues 78 and 79 as influencing antiviral activity. Neutralization experiments with a monoclonal antibody directed against a conserved region from residues 113 to 149 indicated that although this region of the IFN-alpha molecule may be important for antiviral activity, altering residues at sites removed from this region may reduce the effectiveness of the neutralizing antibody. Receptor binding experiments suggested that no single site at either the amino or carboxyl terminus of IFN-alpha alone determines receptor affinity or biological activity: apparently three distinct domains along IFN-alpha are involved (10-35, 78-107, 123-166). Overall, the data indicate that the three sites contribute toward the active configuration of human IFN-alpha.

2',5'-Oligoadenylate Synthetase↗
PubMed1988

The synthetic human growth hormone fragment (32-38) increases glucose uptake in the conscious dog.

hGH32-38 was tested to determine if the peptide could affect hepatic glucose production in the conscious dog under basal conditions (euglycemia) or if it could enhance glucose uptake when hyperglycemia was induced. hGH32-38 (1.6 nmol.kg-1.min-1) or vehicle was infused in a cross-over design study into each of 4 conscious 16 h-fasted dogs for 3 h (0-180 min) following a 40 min control period. At 90 min, plasma glucose was raised to and maintained at 9.4 mmol/l by glucose infusion for 3 h (until 270 min). Neither hGH32-38 nor vehicle infusion had a significant effect on insulin and glucagon levels or on tracer determined [( 3-3H]glucose) glucose production. As a result, neither treatment changed plasma glucose (5.72 +/- 0.17 to 5.78 +/- 0.17 mmol/l with hGH32-38; 5.50 +/- 0.22 to 5.50 +/- 0.17 mmol/l with vehicle). Induction of hyperglycemia (9.4 mmol/l) caused glucagon concentrations to fall similarly to about 50 ng/l with and without hGH32-38. Insulin rose to similar levels in both protocols, yet more glucose was required to maintain the same hyperglycemia with hGH32-38 (135-180 min) (74.9 +/- 12.7 vs 43.7 +/- 7.1 mumol.kg-1.min-1, P less than 0.05). In summary, hGH32-38 significantly increased glucose disposition during hyperglycemia and this effect may be attributed to enhanced insulin action or to an insulin independent action of the peptide.

Animals↗
PubMed1988

Structure/function studies on recombinant human gamma interferon.

Structure/function relationships for human gamma interferon (IFN-gamma) were investigated using recombinant DNA-derived homologues produced in E. coli. The various biological effects examined were antiviral, growth inhibitory and 2-5A synthetase activities, as well as receptor binding characteristics. Specific structural changes led to IFN-gamma homologues with defined alterations in biological activities. Amino acid residue changes at the hydrophobic core of the molecule resulted in two homologues exhibiting loss of affinity for the IFN-gamma receptor and dramatically reduced biological activities. These diminished activities probably relate to the inability of the homologues to form appropriately folded structures. Residue changes at two sites associated with beta-turns on the surface of IFN-gamma likewise resulted in homologues with reduced biological activities. In these cases, the reduced biological activities were not associated with reduced receptor binding. Addition of cysteine-tyrosine-cysteine to the amino-terminus of IFN-gamma, known to perturb the protein conformation, slightly reduced the affinity of the so-derived homologue for the IFN-gamma receptor on T98G cells, and there was concommitant reduction in biological activities. Experiments with a monoclonal antibody that binds to the carboxy-terminus of IFN-gamma indicated that this region of the molecule may not influence antiviral or antiproliferative activities. Overall our data imply that several sites along the IFN-gamma polypeptide contribute to biological activity, and that receptor binding and effector sites are distinct.

2',5'-Oligoadenylate Synthetase↗
PubMed1987

The synthetic 32-46 fragment of human growth hormone increases insulin and glucagon levels in the conscious dog.

Human growth hormone (hGH, 22 K) has an acute insulinlike effect not observed with the 20 K variant form of hGH that lacks amino acids 32 to 46 (deletion peptide, hGH32-46). The possibility that hGH32-46 increases insulin secretion was examined by infusing hGH32-46 (1.6 nmol/kg/min) or saline in a crossover design study into each of four conscious 16-hour-fasted dogs for three hours (0 to 180 minutes) following a 40-minute control period. At 90 minutes, plasma glucose was raised to and maintained at 170 mg/dL by glucose infusion for three hours (until 270 minutes). After a lag period of 30 minutes hGH32-46 infusion caused glucagon to increase (P less than 0.05) by 67 +/- 20 pg/mL and insulin tended to rise by 8 +/- 3 microU/mL. Saline tended to cause glucagon and insulin to decline slightly (by 17 +/- 8 pg/mL and 6 +/- 2 microU/mL); hGH32-46 increased (P less than 0.05) tracer determined (3H-3-glucose) glucose production by 1.13 +/- 0.66 mg/kg/min while saline had no effect. Neither treatment changed plasma glucose (100 +/- 4 to 105 +/- 3 mg/dL with hGH32-46; 99 +/- 4 to 99 +/- 4 mg/dL with saline). Induction of hyperglycemia (168 +/- 2 mg/dL) caused glucagon concentrations to fall similarly to about 50 pg/mL with and without hGH32-46. Insulin rose in both protocols but to a greater extent (P less than 0.05) with hGH32-46 (+67 +/- 18 v +35 +/- 13 microU/mL at 180 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Cytoskeletal association of human alpha-interferon-receptor complexes in interferon-sensitive and -resistant lymphoblastoid cells.

Human Daudi lymphoblastoid cells, which are highly sensitive to the antiproliferative action of human leukocyte alpha-interferon (IFN-alpha), and IFN-resistant and IFN-sensitive Daudi subclones (Cl2 and Cl1, respectively), contain 2300 (Kd = 20 X 10(-12) M), 3000 (Kd = 45 X 10(-12) M), and 3700 (Kd = 52 X 10(-12) M) IFN-alpha binding sites per cell, respectively. Thus, these IFN-sensitive and IFN-resistant cells have similar numbers of high-affinity IFN-alpha receptors. IFN-receptor complexes that are insoluble in Triton X-100 accumulate in IFN-sensitive but not in IFN-resistant cells. The ligand-induced accumulation of Triton-insoluble complexes in IFN-sensitive cells was inhibited by cytochalasin B. This suggests that the solubility change of IFN-receptor complexes results from their interaction with the cytoskeletal matrix. The dissociation of IFN-alpha from IFN-sensitive and IFN-resistant cells can be resolved into fast and slow components. IFN-alpha dissociates more slowly from IFN-sensitive cells than from IFN-resistant cells. Very slow dissociation of IFN-alpha from Triton-insoluble complexes correlates with this difference. These observations suggest that IFN-receptor complexes become coupled to the cytoskeletal matrix in IFN-sensitive but not in IFN-resistant cells, and that such interaction is an important element in the mechanism of the antiproliferative action of IFN-alpha on Daudi cells.

Burkitt Lymphoma↗
PubMed1987

Reevaluation of human alpha interferons against herpesvirus infection of the rabbit eye.

Because of reported differences in potency, recombinant DNA-derived human alpha interferons (IFNs) were reevaluated for use against acute Herpes Simplex Virus type 1 (HSV-1) infection of the rabbit eye. The IFNs used topically were IFN-alpha 2, (IFN-alpha 2) and a consensus of known human IFN-alpha s, designated IFN-alpha Con1. Prophylactic treatment with IFN-alpha Con1 at 1 or 15 X 10(6) U/eye/day beginning 48 hours before HSV-1 inoculation and therapeutic treatment with 5 or 15 X 10(6) U/eye/day beginning 4 hours after inoculation with either IFN-alpha Con1 or IFN-alpha 2 appeared to prevent or significantly reduce the development of corneal epithelial involvement. The effects were dose dependent with no evidence for decreased activity at the higher dose. The duration of HSV-1 shedding into tear film was not significantly reduced.

Acute Disease↗
PubMed1986

Antiviral and antitumor effects of a human interferon analog, IFN-alpha Con 1, assessed in hamsters.

An analog of human alpha-and beta-interferons (IFN-alpha and -beta) (generally consisting of the most frequently observed amino acid residue at each position in the molecule) has pronounced antiviral and antiproliferative activity in human and hamster cells. Intraperitoneal administration of this analog (designated IFN-alpha Con 1) to hamsters at 10(6) to 10(8) U/kg resulted in proportional increases in plasma concentrations through 6 h of monitoring. IFN-alpha Con 1 at these doses effectively limited encephalomyocarditis virus (EMCV) infections of hamsters. A natural human IFN-alpha preparation was also active against virus infections in hamsters. The antitumor activity of IFN-alpha Con 1 and natural human IFN-alpha was assessed in hamsters inoculated with lethal TBD932 lymphosarcoma. Various IFN treatment schedules resulted in prolonged survival following tumor challenge. IFN-alpha Con 1 administered at 10(5) to 10(6) U/hamster daily for 9-12 days following tumor challenge was effective in delaying tumor development, as was a natural human IFN-alpha preparation. The efficacies of combined IFN and cyclophosphamide therapies were determined. Unlike the natural human subtype IFN-alpha A, IFN-alpha Con 1 did not diminish the efficacy of cyclophosphamide (2.5 mg/hamster for 3 days) against the lymphosarcoma. However, an ineffective dose of cyclophosphamide (0.05 mg/hamster for 3 days) when combined with IFN-alpha Con 1 treatment showed enhanced antitumor activity. Combinations of cimetidine (16 mg/hamster for 4 days) and IFN-alpha Con 1 treatment did not prolong survival in this model system.

Animals↗
PubMed1986

Structure and activity of recombinant human interferon-gamma analogs.

We have prepared interferon-gamma (IFN-gamma) analogs to study the structural role of particular amino acids in relation to their effects on antiviral activity. Three IFN-gamma analogs were prepared on the basis of predicted secondary structure. In two of the analogs, [Gln25]IFN-gamma and [Thr45]IFN-gamma, changes were made at residue 25 (Asn to Gln) and at residue 45 (Met to Thr), respectively. [Gln25Lys78]IFN-gamma had two changes, at residue 25 (Asn to Gln) and residue 78 (Asn to Lys). Another analog, [Cys-Tyr-Cys]IFN-gamma, incorporated Cys-Tyr-Cys at the amino terminus. Comparison of the structure and activity of these analogs with that of the natural sequence protein suggested that residues 25 and 78 are at the protein surface and play an important role in antiviral activity. The residue at position 45 was found to be important for maintaining the protein structure, as assessed by circular dichroism spectroscopy. The addition of Cys-Tyr-Cys resulted in a small perturbation of protein structure and a small decrease in antiviral activity.

Amino Acid Sequence↗
PubMed1986

Structure and activity of glycosylated human interferon-gamma.

Structural properties and activity of recombinant human interferon-gamma (IFN-gamma) purified from Chinese hamster ovary (CHO) cells or a natural source were determined and compared with those of Escherichia coli-derived IFN-gamma. One preparation of CHO-derived IFN-gamma showed three bands, with the middle band being a doublet, in a SDS-polyacrylamide gel. The two higher-molecular-weight bands were shown to be glycosylated. Western blot analysis indicated that the three bands are IFN-gamma and lack an intact carboxyl terminus. The circular dichroic (CD) spectra showed that conformation of the CHO-derived IFN-gamma is similar in the native state, in acid, and after renaturation from acid to the E. coli-derived IFN-gamma. These results indicate that neither glycosylation nor carboxy-terminal processing affects conformational properties of the protein, as detected by CD spectroscopy. However, the antiviral activity was fourfold lower for the preparation of CHO-derived IFN-gamma than for the E. coli-derived IFN-gamma. A different preparation or a natural IFN-gamma preparation with less extensive carboxy-terminal processing showed similar conformational properties and antiviral activity to the E. coli-derived IFN-gamma. These results indicate that the carboxyl terminus, but not glycosylation, plays an important role in the antiviral activity of IFN-gamma.

Animals↗
PubMed1986

Antiherpetic effects of a human alpha interferon analog, IFN-alpha Con1, in hamsters.

The efficacy of a novel consensus form of human alpha interferon designated IFN-alpha Con1 was evaluated against herpesvirus infections in vitro and in vivo. At comparable antiviral concentrations, natural lymphoblastoid IFN, IFN-alpha Con1, the molecular subtype IFN-alpha, and the hybrid IFN-alpha AD(Bgl) obtained by recombinant DNA methods conferred similar protection against herpes simplex virus type 1 and type 2 (HSV-2) infections of human cells in vitro. Whereas 7 X 10(5) U of IFN-alpha AD(Bgl) administered in 7 intraperitoneal (i.p.) doses between -4 and 96 h relative to infection protected 90% of mice from a lethal HSV-2 infection, a similar treatment regimen with IFN-alpha Con1 conferred no protection. Systemic HSV-2 infection of hamsters was rapidly lethal, but a single i.p. treatment with 10(6) U of either IFN-alpha Con1 or IFN-alpha AD(Bgl) was highly effective and protected 90 and 75% of animals, respectively, when given 6 h before infection; treatment with IFN-alpha Con1 protected 45% of animals when administered 10 h after infection. In addition, IFN-alpha Con1 was highly protective against acute cervicovaginal HSV-2 infection of hamsters when administered either in a single i.p. dose of 10(6) U at -6 or 10 h relative to infection or in multiple i.p. doses of 10(6) U between -6 and 120 h relative to infection. Protection was manifested by a delay in the onset of and a reduction in duration of infection, a reduction in the number of positive cervicovaginal infections, and an increase in the survival rate.

Animals↗
PubMed1986

Effects of polynucleotide inhibitors on transcriptional events of influenza virions.

Polynucleotide inhibitors of the influenza virion transcriptase, which is activated in vitro by detergent, can be divided into two categories. Polyribonucleotides comprised of adenine and guanine bases or adenine and uracil bases inhibit initiation but not elongation events of transcription. In contrast, polyribonucleotides containing cytidine and uracil or inosine and uracil block both initiation and elongation. Effects on elongation are apparent on addition of polynucleotides at either 5 or 10 min post-initiation. Dose-response studies with these and other polynucleotides have shown that the concentrations causing 50% inhibition of transcription vary considerably with the most potent inhibitor being the modified polymer, poly(C,S4U10).

Orthomyxoviridae↗
PubMed1985

Differential action of six human interferons against two human carcinomas growing in nude mice.

Six different pure human interferons (IFNs), were tested for anti-tumour effect against two human carcinomas, breast and bowel, growing in nude mice, in a total of 36 experiments. The IFN-alpha mixture, analogue and subtypes showed the greatest activity, particularly against the breast cancer xenograft, whereas IFN-beta and IFN-gamma had little effect. However, circulating IFN could be found in the sera of mice treated with all 3 IFN types. In terms of amount of IFN protein, IFN-alpha Con1, an IFN-alpha analogue, was the most effective, a dose of 0.1 micrograms/mouse/day being sufficient to induce breast tumour regression, and IFN-gamma the least effective, a dose of 10 micrograms/mouse/day having no effect on the same tumour. A more detailed comparison of 2 IFN-alpha subtypes showed that a daily dose of 1 microgram IFN-alpha A was more effective than the same dose of IFN-alpha D, but as this IFN had approximately 30 times less antiviral activity on human cells than IFN-alpha D, these IFNs were probably at least equally effective in terms of human cell units. IFN-alpha D stimulated mouse spleen natural killer cell activity but it was not clear whether this stimulation was involved in anti-tumour activity. We conclude that this model system is useful for investigating direct anti-tumour activity of a wide range of IFN types and subtypes.

2',5'-Oligoadenylate Synthetase↗